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For middle-aged patients with presbyopia, wearing OK contact lenses overnight can restore up-close vision in one eye, according to the study by Paul Gifford, PhD, FAAO, and Helen A Swarbrick, PhD, FAAO, of University of New South Wales, Sydney. "The authors have shown the feasibility of correcting one eye for near vision through OK, in which overnight contact lens wear shapes the cornea of one eye to allow in-focus near vision for reading," comments Anthony Adams, OD, PhD, Editor-in-Chief of Optometry and Vision Science.

Overnight OK Lens Wear Restores Near Vision in One EyeThe study included 16 middle-aged patients (43 to 59 years) with age-related loss of near vision, or presbyopia. Presbyopia is caused by age-related loss of flexibility in the cornea—the transparent front part that lets light into the eye.

Orthokeratology is a clinical technique to correct vision using specially designed rigid contact lenses to manipulate the shape of the cornea. Dr. Adams likens OK therapy to orthodontic treatment using braces to change the alignment of the teeth.

Drs. Gifford and Swarbick evaluated a "monocular" technique, with patients wearing a custom-made OK lens in one eye overnight for one week. To preserve normal distance vision, the other eye was left untreated.

In all patients, the monocular OK technique was successful in restoring near vision in the treated eye. The improvement was apparent on the first day after overnight OK lens wear, and increased further during the treatment week. Eye examination confirmed that the OK lenses altered the shape of the cornea, as they were designed to do.

Nightly Lens Wear Needed to Retain CorrectionVision in the untreated eye was unaffected, and all patients retained normal distance vision with that eye; essentially this gives the patient the dequivalent of ‘monovision’ that is usually done with contact lenses or surgery. To retain the correction in near vision, patients had to continue wearing their OK lenses every night. Dr. Adams likens this ongoing treatment to the "retainer" that orthodontic patients have to wear nightly. As expected, when patients stopped wearing their OK lens after the treatment week, presbyopia rapidly returned.

By about age 45 to 50, most people need bifocals or some other form of vision correction to restore vision for reading and other up-close tasks. Alternatives for presbyopia have been introduced, including fitting a contact lens for distance vision in one eye and a lens for near vision in the other eye. This is the so called monovision, now the authors show it can be achieved without the need to wear a contact lens during the day. "However, the chief problem with monovision for many people is that their stereoscopic 3D vision is degraded and many find that hard to tolerate," according to Dr. Adams.

Although overnight OK is not a new technique, it has been mainly used to reduce nearsightedness (myopia) in younger patients. The new study shows that OK is similarly effective in changing corneal shape, and achieving desired correction in near vision, in older patients with presbyopia.

The new study suggests that overnight OK lenses are a feasible alternative for correction of presbyopia, "sufficient to provide functional near vision correction white retaining good distance visual acuity," Drs. Gifford and Swarbick write. The technique is safe, with the cornea returning to its previous shape about a week after the patient stops wearing the lenses.

"This study demonstrates that OK is quite viable as a nonsurgical option for monovision that does not require wearing contact lenses during the day, although it does require 'retainer' orthokeratology contact lenses to be worn overnight," Dr. Adams adds. "This possibility will certainly appeal to many people, especially since the changes in the corneal curvature of the treated eye are fully reversible."

About Optometry and Vision ScienceOptometry and Vision Science, official journal of the American Academy of Optometry, is the most authoritative source for current developments in optometry, physiological optics, and vision science. This frequently cited monthly scientific journal has served primary eye care practitioners for more than 75 years, promoting vital interdisciplinary exchange among optometrists and vision scientists worldwide.

About the American Academy of OptometryFounded in 1922, the American Academy of Optometry is committed to promoting the art and science of vision care through lifelong learning. All members of the Academy are dedicated to the highest standards of optometric practice through clinical care, education or research.

About Lippincott Williams & WilkinsLippincott Williams & Wilkins (LWW) is a leading international publisher of trusted content delivered in innovative ways to practitioners, professionals and students to learn new skills, stay current on their practice, and make important decisions to improve patient care and clinical outcomes.

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